Vapor deposition of thin films comprising gold

ABSTRACT

Vapor deposition processes for forming thin films comprising gold on a substrate in a reaction space are provided. The processes can be cyclical vapor deposition processes, such as atomic layer deposition (ALD) processes. The processes can include contacting the substrate with a gold precursor comprising at least one sulfur donor ligand and at least one alkyl ligand, and contacting the substrate with a second reactant comprising ozone. The deposited thin films comprising gold can be uniform, continuous, and conductive at very low thicknesses.

REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. application Ser. No.17/330,994, filed May 26, 2021, which is a continuation of U.S.application Ser. No. 16/178,199, filed Nov. 1, 2018, now U.S. Pat. No.11,047,046, which is a continuation of U.S. application Ser. No.15/417,001, filed Jan. 26, 2017, now U.S. Pat. No. 10,145,009, each ofwhich is hereby incorporated by reference in its entirety.

PARTIES OF JOINT RESEARCH AGREEMENT

The invention claimed herein was made by, or on behalf of, and/or inconnection with a joint research agreement between the University ofHelsinki and ASM Microchemistry Oy. The agreement was in effect on andbefore the date the claimed invention was made, and the claimedinvention was made as a result of activities undertaken within the scopeof the agreement.

BACKGROUND OF THE INVENTION Field of the Invention

The present disclosure relates generally to the field of vapor phasedeposition, particularly cyclical vapor deposition of thin filmscomprising gold.

Description of the Related Art

Thin films comprising gold have desirable electronic and plasmonicproperties for a variety of applications in a variety of fields,including photonics, MEMS devices, electronic components, electrochromicdevices, photovoltaics, photocatalysis, and more. However, reliabledeposition of thin films comprising gold by cyclical vapor depositionprocesses has proven difficult, particularly with respect to depositionof continuous and conducting thin films comprising gold.

SUMMARY OF THE INVENTION

According to some embodiments processes for forming thin filmscomprising gold on a substrate in a reaction space are provided herein.In some embodiments the process may comprise alternately andsequentially contacting the substrate with a vapor phase gold precursorand a vapor phase second reactant, wherein the vapor phase goldprecursor comprises at least one ligand comprising sulfur or selenium,and at least one alkyl ligand, and wherein the gold precursor and thesecond reactant react to thereby form the thin film comprising gold.

In some embodiments alternately and sequentially contacting thesubstrate with a vapor phase gold precursor and a vapor phase secondreactant may comprise a deposition cycle that is repeated two or moretimes. In some embodiments, the deposition cycle may further compriseremoving excess vapor phase gold precursor and reaction byproducts, ifany, from the reaction space after contacting the substrate with thevapor phase gold precursor. In some embodiments, the deposition cyclemay further comprise removing excess second reactant and reactionbyproducts, if any, from the reaction space after contacting thesubstrate with the second reactant.

According to some embodiments the gold of the gold precursor has anoxidation state of +III. In some embodiments, the ligand comprisingsulfur or selenium comprises sulfur. In some embodiments, the ligandcomprising sulfur or selenium comprises selenium. In some embodiments,the gold precursor comprises one or more additional neutral adducts. Insome embodiments, the gold precursor comprises a diethyldithiocarbamatoligand. In some embodiments, the gold precursor comprisesMe₂Au(S₂CNEt₂). In some embodiments, the second reactant comprisesoxygen. In some embodiments, the second reactant comprises a reactivespecies of oxygen. In some embodiments, the second reactant comprisesozone.

According to some embodiments, the process has a deposition temperatureof from about 120° C. to about 220° C. In some embodiments, the thinfilm comprising gold is continuous when it reaches a thickness of about20 nm. In some embodiments, the thin film comprising gold has athickness of from about 20 nm to about 50 nm. In some embodiments, thethin film comprising gold has a resistivity of less than about 20 μΩcm.In some embodiments, the thin film comprising gold has a growth rate ofmore than about 0.8 Å per deposition cycle. In some embodiments, theprocess is an atomic layer deposition (ALD) process. In someembodiments, the process is a cyclical chemical vapor deposition (CVD)process.

According to some embodiments atomic layer deposition (ALD) processesfor forming thin films comprising gold on a substrate in a reactionspace are provided. In some embodiments the process may comprise aplurality of deposition cycles, wherein at least one deposition cyclecomprises alternately and sequentially contacting the substrate with avapor phase gold precursor and a vapor phase second reactant, whereinthe deposition cycle is repeated two or more times to form the thin filmcomprising gold, wherein the gold of the vapor phase gold precursor hasan oxidation state of +III and the vapor phase gold precursor comprisesat least one sulfur donor ligand and at least one alkyl ligand.

According to some embodiments, the gold precursor comprisesMe₂Au(S₂CNEt₂). In some embodiments, the second reactant comprisesozone. In some embodiments, the thin film comprising gold is continuouswhen it reaches a thickness of about 20 nm. In some embodiments, thethin film comprising gold is continuous after 100 deposition cycles.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood from the Detailed Descriptionand from the appended drawings, which are meant to illustrate and not tolimit the invention, and wherein:

FIG. 1 is a process flow diagram generally illustrating a cyclical vapordeposition process for depositing thin films comprising gold;

FIG. 2 is a process flow diagram generally illustrating an atomic layerdeposition process for depositing thin films comprising gold;

FIG. 3 illustrates a thermogravimetric curve for Me₂Au(S₂CNEt₂);

FIG. 4A is a plot of thin film growth rate versus deposition temperaturefor thin films comprising gold deposited by cyclical vapor depositionprocesses as described herein and according to some embodiments;

FIG. 4B is a plot of thin film thickness versus film distance from thegold precursor inlet in a reaction chamber for thin films comprisinggold deposited at temperatures from 120° C. to 200° C. by cyclical vapordeposition processes as described herein and according to someembodiments;

FIG. 4C is a plot of thin film resistivity versus deposition temperaturefor thin films comprising gold deposited at temperatures from 120° C. to200° C. by cyclical vapor deposition processes as described herein andaccording to some embodiments;

FIG. 4D is an X-ray diffractogram for thin films comprising golddeposited at temperatures from 120° C. to 200° C. by cyclical vapordeposition processes as described herein and according to someembodiments;

FIGS. 5A-D are scanning electron microscope (SEM) images of thin filmscomprising gold deposited at temperatures from 120° C. to 200° C. bycyclical vapor deposition processes as described herein and according tosome embodiments;

FIG. 6A is a plot of thin film growth rate versus gold precursor pulselength for thin films comprising gold deposited at a temperature of 180°C. by cyclical vapor deposition processes as described herein andaccording to some embodiments;

FIG. 6B is a plot of thin film thickness versus film distance from thegold precursor inlet in a reaction chamber for thin films comprisinggold deposited with gold precursor pulse lengths of 1 second and 2seconds by cyclical vapor deposition processes as described herein andaccording to some embodiments;

FIG. 6C is a plot of thin film resistivity versus gold precursor pulselength for thin films comprising gold deposited by cyclical vapordeposition processes as described herein and according to someembodiments;

FIG. 7A is a plot of thin film thickness versus number of depositioncycles for thin films comprising gold deposited by cyclical vapordeposition processes as described herein and according to someembodiments;

FIGS. 7B-D are SEM images of thin films comprising gold deposited withbetween 50 and 500 cycles by cyclical vapor deposition processes asdescribed herein and according to some embodiments;

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Thin films comprising gold, particularly continuous metallic gold thinfilms deposited according to some embodiments as described herein, havea wide variety of potential applications. For example, in the field ofplasmonic sensing, thin films comprising gold deposited by someembodiments as described herein may be useful in surface-enhanced Ramanspectroscopy (SERS). The unique plasmonic properties of thin filmscomprising gold make such films highly desirable for manynext-generation electronic and photonic devices. Gold is also a highlyefficient conductor and can carry very small currents while remainingrelatively free of corrosion as compared to other metallic thin films.Therefore, thin films comprising gold deposited by some embodiments asdescribed herein may be useful in a variety of electronic component anddevice applications, including, for example, nanofabricatedsemiconductor devices.

Continuous and conducting thin films comprising gold deposited by someembodiments as described herein may also have applications inmicroelectromechanical systems (MEMS) devices, such as radio-frequency(RF) MEMS devices, due to such films high electrical conductivity. RFMEMS devices including continuous and conducting thin films comprisinggold deposited by some embodiments as described herein can operate atgigahertz frequencies, allowing for large bandwidth and extremely highsignal-to-noise rations. Continuous thin films comprising gold depositedby some embodiments as described herein may also be useful in inertialMEMS to increase the mass of a proof-mass for achieving high sensitivityin accelerometers. Such thin films comprising gold can be used invariable capacitors, chemical and biological sensors, and opticaldetectors.

Thin films comprising gold deposited according to processes describedherein may also be useful in electrochromic devices, photovoltaics, andphotocatalysis, among other applications.

According to some embodiments thin films comprising gold and processesfor forming thin films comprising gold are provided. In someembodiments, thin films comprising gold deposited according to theprocesses described herein may be metallic and may be continuous andconducting.

In some embodiments, thin films comprising gold are deposited on asubstrate by vapor deposition processes. For example, in someembodiments a thin film comprising gold may be deposited by a depositionprocess utilizing surface-controlled reactions in which a gold precursoron the substrate reacts with an second reactant to form the filmcomprising gold, for example as in an atomic layer deposition typeprocess. In some embodiments, the vapor deposition process may be athermal deposition process. In some embodiments, the vapor depositionprocess may be a plasma deposition process. However, in some embodimentsthe vapor deposition process does not utilize plasma. In someembodiments, the deposition process may be a cyclical depositionprocess, for example an atomic layer deposition (ALD) process or acyclical chemical vapor deposition (CVD) process. In some embodiments, aprocess for depositing a thin film comprising gold may comprisealternately and sequentially contacting a substrate with a first vaporphase gold reactant and a second reactant.

In some embodiments, the deposition process may utilize anorganometallic gold precursor and a second reactant. In someembodiments, the gold of the organometallic gold precursor may have anoxidation state of +III. In some embodiments, the organometallic goldprecursor may comprise sulfur. In some embodiments, the organometallicgold precursor comprises at least one ligand comprising sulfur and atleast one alkyl ligand. For example, when a gold precursor is utilizedin a process as described herein, and the said gold precursor does notcomprise at least one ligand comprising sulfur and at least one alkylligand, such a process may not deposit a continuous film comprisinggold, or will produce a continuous film only at high film thicknesses.It was thus unexpectedly found that utilizing a gold precursorcomprising at least one ligand comprising sulfur and at least one alkylligand, such as a gold precursor comprising Me₂Au(S₂CNEt₂), allows fordeposition of a high quality thin films comprising gold at relativelylow film thicknesses, for example a continuous gold thin film having arelatively low film thickness. In some embodiments, the organometallicgold precursor may comprise Me₂Au(S₂CNEt₂). In some embodiments, thesecond reactant may comprise oxygen. In some embodiments, the secondreactant may comprise a reactive form of oxygen, for example ozone. Insome embodiments a process for depositing a thin film comprising goldmay utilize a gold precursor comprising at least one ligand comprisingsulfur, at least one alkyl ligand, wherein the oxidation state of thegold of the gold precursor is +III, and an second reactant comprisingozone.

In some embodiments, the deposited thin film may comprise gold. In someembodiments, a thin film comprising metallic gold may be deposited. Insome embodiments, the deposited thin film comprising gold may comprisean amount of oxygen. In some embodiments, the deposited thin filmcomprising gold may be continuous. In some embodiments the depositedfilm comprising gold may be continuous at a thickness of less than about50 nm, less than about 40 nm, less than about 30 nm, or less than about20 nm or thinner. In some embodiments a continuous film comprising goldmay be deposited by a deposition process comprising fewer than about 500deposition cycles, fewer than about 400 deposition cycles, fewer thanabout 300 deposition cycles, fewer than about 200 deposition cycles, orfewer than about 100 deposition cycles or fewer.

In some embodiments, the deposited film comprising gold may be aconducting film. In some embodiments the deposited film comprising goldmay have a resistivity of less than about 20 μΩcm, less than about 15μΩcm, less than about 10 μΩcm, less than about 5 μΩcm or fewer.

Vapor Deposition of Thin Films Comprising Gold

In some embodiments, films comprising gold are deposited by an atomiclayer deposition-type process. Atomic layer deposition (ALD) typeprocesses are based on controlled, self-limiting surface reactions ofprecursor chemicals, or reactants. Gas phase reactions are avoided byalternately and sequentially contacting the substrate with theprecursors. Vapor phase reactants are separated from each other on thesubstrate surface, for example, by removing excess reactants and/orreactant byproducts from substrate surface of interest between reactantpulses. In some embodiments, one or more substrate surfaces arealternately and sequentially contacted with two or more vapor phaseprecursors, or reactants. Contacting a substrate surface with avapor-phase reactant means that the reactant vapor is in contact withthe substrate surface for a limited period of time. In other words, itcan be understood that the substrate surface is exposed to each vaporphase reactant for a limited period of time.

Briefly, a substrate is heated to a suitable deposition temperature,generally at lowered pressure. Deposition temperatures are generallymaintained below the thermal decomposition temperature of the reactantsbut at a high enough level to avoid condensation of reactants and toprovide the activation energy for the desired surface reactions. Ofcourse, the appropriate temperature window for any given ALD reactionwill depend upon the surface termination and reactant species involved.Here, the temperature varies depending on the precursors being used andis generally at or below about 700° C., in some embodiments thedeposition temperature is generally at or above about 100° C. for vapordeposition processes, in some embodiments the deposition temperature isbetween about 100° C. and about 250° C., and in some embodiments thedeposition temperature is between about 120° C. and about 200° C. Insome embodiments, the deposition temperature is below about 500° C.,below about 400° C. or below about 300° C. In some instances thedeposition temperature can be below about 200° C., below about 150° C.or below about 100° C., for example, if additional reactants or reducingagents, such as reactants or reducing agents comprising hydrogen, areused in the process.

The surface of the substrate is contacted with a first vapor phasereactant or precursor. In some embodiments a pulse of vapor phase firstreactant is provided to a reaction space containing the substrate (forexample, in time divided ALD). In some embodiments the substrate ismoved to a reaction space containing vapor phase first reactant (forexample, in space divided ALD, also known as spatial ALD). Conditionscan be selected such that no more than about one monolayer of the firstreactant or a species thereof is adsorbed on the first surface of thesubstrate in a self-limiting manner. However, in some arrangementshybrid CVD/ALD, or cyclical CVD, processes can allow overlap of thedifferent mutually reactive reactants over the substrate and thus canproduce more than a monolayer per cycle. The appropriate contactingtimes can be readily determined by the skilled artisan based on theparticular circumstances. Excess first reactant and reaction byproducts,if any, are removed from the substrate surface, such as by purging withan inert gas or by removing the substrate from the presence of the firstreactant.

For ALD processes, in which overlap between the reactants is minimizedor avoided, vapor phase precursors and/or vapor phase byproducts areremoved from the substrate surface, such as by evacuating a chamber witha vacuum pump and/or by purging (for example, replacing the gas inside areactor with an inert gas such as argon or nitrogen). Supply of thereactant to the substrate surface is typically stopped during theremoval periods, and may be shunted to a different chamber or to avacuum pump during the removal periods. Typical removal times are fromabout 0.05 to 20 seconds, from about 1 to 10 seconds, or from about 1 to2 seconds. However, other removal times can be utilized if necessary,such as where highly conformal step coverage over extremely high aspectratio structures or other structures with complex surface morphology isneeded.

The surface of the substrate is contacted with a vapor phase secondreactant or precursor. In some embodiments, a pulse of a second reactantis provided to a reaction space containing the substrate. In someembodiments, the substrate is moved to a reaction space containing thevapor phase second reactant. Excess second reactant and gaseousbyproducts of the surface reaction, if any, are removed from thesubstrate surface. Contacting and removing are repeated until a thinfilm of the desired thickness has been formed on the substrate, witheach cycle leaving no more than about a molecular monolayer in an ALD orALD type process, or one or more molecular monolayers in a hybridCVD/ALD, or cyclical CVD process. Additional phases comprisingalternately and sequentially contacting the surface of a substrate withother reactants can be included to form more complicated materials, suchas alloys comprising two or more metals, or composite materialscomprising gold and some other compound or compounds.

As mentioned above, each phase of each cycle can be self-limiting forALD processes. An excess of reactants is supplied in each phase tosaturate the susceptible substrate surfaces. Surface saturation ensuresreactant occupation of all available reactive sites (subject, forexample, to physical size or “steric hindrance” restraints) and thusensures excellent step coverage. Typically, less than one molecularlayer of material is deposited with each cycle, however, in someembodiments more than one molecular layer is deposited during the cycle.

Removing excess reactants can include evacuating some of the contents ofa reaction space and/or purging a reaction space with helium, nitrogen,argon or another inert gas. In some embodiments, purging can compriseturning off the flow of the reactive gas while continuing to flow aninert carrier gas to the reaction space. For example, in someembodiments an inert carrier gas may be flown continuously throughoutthe deposition process while the precursors or reactants may beintermittently supplied to the reaction space.

The substrate can comprise various types of materials. Whenmanufacturing integrated circuits, the substrate typically comprises anumber of thin films with varying chemical and physical properties. Insome embodiments, the substrate may comprise silicon or silicon oxide,for example native oxide or thermal oxide. In some embodiments, thesubstrate may comprise glass. In some embodiments, the substrate maycomprise one or more oxide materials, for example a metal oxidematerial. In some embodiments, the substrate may comprise a dielectricmaterial. In some embodiments, the substrate may comprise a metal, or ametallic film, such as a metal nitride, metal carbide, metal silicide,or mixtures thereof. In some embodiments, the substrate may be asemiconductor substrate. In some embodiments, the substrate may compriseone or more three-dimensional structures. In some embodiments, one ormore structures may have an aspect ratio of from 1:1 to 10:1 or greater.In some embodiments, the substrate may comprise an integrated circuitworkpiece. In some embodiments, the substrate does not comprisesemiconductor substrate or wafer.

The precursors employed in vapor deposition processes may be solid,liquid or gaseous materials under standard conditions (room temperatureand atmospheric pressure), provided that the precursors are in vaporphase before they are contacted with the substrate surface. Contacting asubstrate surface with a vaporized precursor means that the precursorvapor is in contact with the substrate surface for a limited period oftime. Typically, the contacting time is from about 0.05 to 10 seconds.However, depending on the substrate type, its surface area, and/or thesize of the chamber the contacting time may be even higher than 10seconds. Contacting times can be on the order of minutes in some cases,particularly for batch deposition processes on multiple substrates. Theoptimum contacting time can be determined by the skilled artisan basedon the particular circumstances.

The mass flow rate of the precursors can also be determined by theskilled artisan. In some embodiments, the flow rate of precursors isbetween about 1 and 1000 sccm without limitation, more particularlybetween about 100 and 500 sccm for a single wafer deposition reactor. Insome embodiments, the flow rate may be less than 100 sccm, less than 75sccm, or less than 50 sccm.

The pressure in a reaction chamber is typically from about 0.01 mbar toabout 20 mbar, or from about 1 mbar to about 10 mbar. In someembodiments the reaction chamber pressure may be from about 0.01 mbar toabout atmospheric pressure

Before starting the deposition of the film, the substrate is typicallyheated to a suitable growth temperature. The growth temperature variesdepending on the type of thin film formed, chemical and physicalproperties of the precursors, etc. The growth temperature can be lessthan the crystallization temperature for the deposited materials suchthat an amorphous thin film is formed or it can be above thecrystallization temperature such that a crystalline thin film is formed.The deposition temperature may vary depending on a number of factorssuch as, and without limitation, the reactant precursors, the pressure,flow rate, the arrangement of the reactor, crystallization temperatureof the deposited thin film, and the composition of the substrateincluding the nature of the material to be deposited on. The specificgrowth temperature may be selected by the skilled artisan.

In some embodiments, the substrate temperature is high enough to supportthermal ALD for the reactants of interest. For example, the substratetemperature is generally greater than about 100° C. and at or belowabout 700° C. In some embodiments, the substrate temperature is betweenabout 100° C. and about 250° C., and in some embodiments the substratetemperature is between about 120° C. and about 200° C. In someembodiments, the substrate temperature is below about 500° C., belowabout 400° C. or below about 300° C. In some instances, the substratetemperature can be below about 200° C., below about 150° C. or belowabout 100° C.

In some embodiments a thin film comprising gold may be formed on asubstrate by a process comprising at least one deposition cycle, thedeposition cycle comprising alternately and sequentially contacting thesubstrate with a vapor phase gold precursor and a vapor phase secondreactant. In some embodiments the deposition cycle may be repeated twoor more times. In some embodiments, the deposition cycle may be repeatedtwo or more times sequentially. In some embodiments excess goldprecursor and reaction byproducts, if any, may be removed subsequent tocontacting the substrate with a vapor phase gold precursor and prior tocontacting the substrate with the vapor phase second reactant. In someembodiments excess second reactant and reaction byproducts, if any, maybe removed subsequent to contacting the substrate with a vapor phasegold precursor and prior to beginning another deposition cycle. In someembodiments, the substrate may be contacted with a purge gas subsequentto contacting the substrate with the vapor phase gold precursor andprior to contacting the substrate with the vapor phase second reactant.In some embodiments, the substrate may be contacted with a purge gassubsequent to contacting the substrate with the vapor phase secondreactant prior to beginning another deposition cycle.

The thin film comprising gold formed according to some embodiments isbetween about 20 nm and about 50 nm; however, the actual thicknesschosen may be selected based on the intended application of the thinfilm. In some embodiments, it is desirable to ensure that all or most ofa target substrate surface is covered by the thin film comprising gold.In some embodiments, it is desirable to form a continuous filmcomprising gold. In such cases, it may be desirable to form a filmcomprising gold that is at least about 10 nm thick, at least about 20 nmthick, at least about 30 nm thick, at least about 40 nm, or at leastabout 50 nm thick. In some embodiment's thickness great than 50 nm maybe desired, for example thicknesses of greater than 100 nm, greater than250 nm, or greater than 500 nm or greater. However, in some otherembodiments it may be desirable to form a non-continuous thin filmcomprising gold, or a thin film comprising separate islands ornanoparticles comprising gold.

In some embodiments it may be desirable to form a thin film comprisinggold with a certain number of deposition cycles, for example more thanabout 50 cycle, more than about 100 cycles, more than about 250 cycles,or more than about 500 cycles or more. In some embodiments, thedeposition process may include any number of deposition cycles.

Reactors capable of being used to grow thin films can be used for thedeposition. Such reactors include ALD reactors, as well as CVD reactorsequipped with appropriate equipment and means for providing theprecursors. According to some embodiments, a showerhead reactor may beused.

Examples of suitable reactors that may be used include commerciallyavailable single substrate (or single wafer) deposition equipment suchas Pulsar® reactors (such as the Pulsar® 2000 and the Pulsar® 3000 andPulsar® XP ALD), and EmerALD® XP and the EmerALD® reactors, availablefrom ASM America, Inc. of Phoenix, Ariz. and ASM Europe B.V., Almere,Netherlands. Other commercially available reactors include those fromASM Japan K.K (Tokyo, Japan) under the tradename Eagle® XP and XP8.

In some embodiments, a batch reactor may be used. Suitable batchreactors include, but are not limited to, Advance® 400 Series reactorscommercially available from and ASM Europe B.V (Almere, Netherlands)under the trade names A400 and A412 PLUS. In some embodiments a verticalbatch reactor is utilized in which the boat rotates during processing,such as the A412. Thus, in some embodiments the wafers rotate duringprocessing. In other embodiments, the batch reactor comprises aminibatch reactor configured to accommodate 10 or fewer wafers, eight orfewer wafers, 6 or fewer wafers, 4 or fewer wafers, or 2 wafers. In someembodiments in which a batch reactor is used, wafer-to-wafer uniformityis less than 3% (1 sigma), less than 2%, less than 1% or even less than0.5%.

The deposition processes described herein can optionally be carried outin a reactor or reaction space connected to a cluster tool. In a clustertool, because each reaction space is dedicated to one type of process,the temperature of the reaction space in each module can be keptconstant, which improves the throughput compared to a reactor in whichthe substrate is heated up to the process temperature before each run.Additionally, in a cluster tool it is possible to reduce the time topump the reaction space to the desired process pressure levels betweensubstrates.

A stand-alone reactor can be equipped with a load-lock. In that case, itis not necessary to cool down the reaction space between each run. Insome embodiments a deposition process for depositing a thin filmcomprising gold may comprise a plurality of deposition cycles, forexample ALD cycles.

In a second phase, the substrate is contacted with a second reactant,for example a second reactant comprising ozone that may convert adsorbedfirst precursor to gold material. Contacting the substrate with a secondreactant and thereafter removing excess second reactant and reactionbyproducts, if any, from the substrate surface may be considered a phaseand may be referred to as a second phase, second reactant phase, secondprecursor phase, etc.

One or more of the precursors may be provided with the aid of a carriergas, such as N₂, Ar, or He. Additional phases may be added and phasesmay be removed as desired to adjust the composition of the final film.The terms “first” and “second” may be applied to any particularprecursor or reactant depending on the sequencing of any particularembodiment. For example, depending on the embodiment the first reactantcan be either a gold precursor or a second reactant.

Referring to FIG. 1 and according to some embodiments a thin filmcomprising gold is deposited on a substrate in a reaction space by acyclical vapor deposition process 100 comprising at least one depositioncycle comprising:

contacting the surface of the substrate with a vapor phase goldprecursor comprising at least one sulfur donor ligand (that is, a ligandbonded to a gold atom through a sulfur atom) and at least one alkylligand at block 110;

removing any excess gold precursor and reaction byproducts, if any, fromthe surface at block 120;

contacting the surface of the substrate with a vapor phase secondreactant at block 130;

removing any excess second recant and reaction byproducts, if any, fromthe surface of the substrate at block 140; and

optionally repeating the contacting and removing step at block 150 toform a thin film comprising gold of a desired thickness.

In some embodiments the above described cyclical deposition process 100may be an ALD type process. In some embodiments the cyclical depositionprocess 100 may be an ALD process. In some embodiments theabove-described cyclical deposition 100 may be a hybrid ALD/CVD orcyclical CVD process.

Although the illustrated deposition cycle begins with contacting thesurface of the substrate with the vapor phase gold precursor, in otherembodiments the deposition cycle may begin with contacting the surfaceof the substrate with the second reactant. It will be understood by theskilled artisan that if the surface of the substrate is contacted with afirst precursor and that precursor does not react then the process willbegin when the next precursor is provided.

In some embodiments removing the precursors or reactant and any excessreaction byproducts at blocks 120 and 140 may comprise purging thereaction space or reaction chamber. Purging the reaction chamber maycomprise the use of a purge gas and/or the application of a vacuum tothe reaction space. Where a purge gas is used, the purge gas may flowcontinuously or may be flowed through the reaction space only after theflow of a reactant gas has been stopped and before the next reactant gasbegins flowing through the reaction space. It is also possible tocontinuously flow a purge or non-reactive gas through the reactionchamber so as to utilize the non-reactive gas as a carrier gas for thevarious reactive species. Thus, in some embodiments, a gas, such asnitrogen, continuously flows through the reaction space while the goldprecursor and second reactant are pulsed as necessary into the reactionchamber. Because the carrier gas is continuously flowing, removingexcess reactant or reaction by-products is achieved by merely stoppingthe flow of reactant gas into the reaction space.

In some embodiments removing the precursors or reactant and any excessreaction byproducts at blocks 120 and 140 may comprise moving thesubstrate from a first reaction chamber to a second, different reactionchamber containing a purge gas. In some embodiments removing theprecursors or reactant and any excess reaction byproducts at blocks 120and 140 may comprise moving the substrate from a first reaction chamberto a second, different reaction chamber under a vacuum. In someembodiments removing the precursors or reactant and any excess reactionbyproducts at blocks 120 and 140 may comprise moving the substrate froma first precursor zone to a second, different precursor zone. The twozones can separated, for example, by a buffer zone comprising of a purgegas and/or vacuum.

In some embodiments the deposited thin film comprising gold may besubjected to a treatment process after deposition. In some embodimentsthis treatment process may, for example, enhance the conductivity orcontinuity of the deposited thin film comprising gold. In someembodiments a treatment process may comprise, for example an annealprocess. In some embodiments the thin film comprising gold may beannealed in an atmosphere comprising one or more annealing gases, forexample a gas comprising hydrogen.

Referring to FIG. 2 and according to some embodiments a thin filmcomprising gold is deposited on a substrate in a reaction space by anatomic layer deposition process 200 comprising at least one depositioncycle comprising:

contacting the surface of the substrate with a vapor phase goldprecursor comprising Me₂Au(S₂CNEt₂) at block 210;

removing any excess gold precursor and reaction byproducts, if any, fromthe surface at block 220;

contacting the surface of the substrate with a vapor phase secondreactant comprising ozone at block 230;

removing any excess oxygen recant and reaction byproducts, if any, fromthe surface of the substrate at block 240; and

optionally repeating the contacting and removing step at block 250 toform a thin film comprising gold of a desired thickness.

In some embodiments a thin film comprising gold is formed on a substrateby an ALD type process comprising at least one deposition cyclecomprising:

contacting the surface of a substrate with a vapor phase gold precursorcomprising at least one sulfur donor ligand and at least one alkylligand to form at most a molecular monolayer of gold precursor or aspecies thereof on the substrate;

removing excess gold precursor and reaction by products, if any, fromthe surface;

contacting the surface of the substrate with a vapor phase secondreactant comprising ozone;

removing from the surface any excess second reactant and any gaseousby-products formed in the reaction between the gold precursor layer andthe second reactant comprising ozone.

The contacting and removing steps can be repeated until a thin filmcomprising gold of the desired thickness has been formed.

In some embodiments a thin film comprising gold deposition process mayfurther comprise subjecting the substrate to a pretreatment processprior to contacting the substrate with the first vapor phase goldprecursor. In some embodiments a pretreatment process may compriseexposing the substrate to a pretreatment reactant. In some embodimentsthe pretreatment reactant may remove undesirable contaminants or mayprepare the surface for subsequent deposition of the thin filmcomprising gold. In some embodiments the pretreatment reactant maycomprise, for example, HCl, HF, or a reactive species, such as plasma.

Gold Precursors

In some embodiments the gold precursor used in a vapor depositionprocess for depositing a thin film comprising gold may comprise anorganometallic compound. In some embodiments the gold precursor maycomprise an organometallic compound comprising sulfur. In someembodiments the gold precursor may comprise at least one ligandcomprising sulfur, such as a sulfur donor ligand, and at least one alkylligand, for example, at least one methyl, or ethyl ligand. As usedherein, a sulfur donor ligand is a ligand that is bonded via a sulfuratom. In some embodiments the gold of the gold precursor may comprise anoxidation state of +III. In some embodiments the gold precursor maycomprise at least one sulfur donor ligand and two independently selectedalkyl ligands. In some embodiments the gold precursor comprises at leastone bidentate ligand comprising sulfur, such as bidentate sulfur donorligand. In some embodiments the bidentate sulfur donor ligand comprisesone sulfur atom, or in some embodiments two sulfur atoms. In someembodiments the bidentate sulfur donor ligand comprises one sulfur atom,such as a donor sulfur atom bonded to gold, and one other atom, such asnitrogen, selenium, or oxygen atom bonded to gold. In some embodimentsthe bidentate sulfur donor ligand makes the compound thermally stable.In some embodiments the gold precursor comprises at least twomonodentate ligands comprising sulfur, such as sulfur donor ligands. Insome embodiments the gold precursor comprises at least two monodentateligands comprising sulfur, such as two sulfur donor ligands and an alkylligand.

In some embodiments the gold precursor may comprise an organometalliccompound comprising selenium. In some embodiments the gold precursor maycomprise at least one ligand comprising selenium, such as a seleniumdonor ligand, and at least one alkyl ligand, for example, at least onemethyl, or ethyl ligand. As used herein, a selenium donor ligand is aligand that is bonded via a selenium atom. In some embodiments the goldof the gold precursor may comprise an oxidation state of +III. In someembodiments the gold precursor may comprise at least one selenium donorligand and two independently selected alkyl ligands. In some embodimentsthe gold precursor comprises at least one bidentate ligand comprisingselenium, such as bidentate selenium donor ligand. In some embodimentsthe bidentate selenium donor ligand comprises one selenium atom, or insome embodiments two selenium atoms. In some embodiments the bidentateselenium donor ligand comprises one v atom, such as a donor seleniumatom bonded to gold, and one other atom, such as nitrogen, selenium, oroxygen atom bonded to gold. In some embodiments the bidentate seleniumdonor ligand makes the compound thermally stable. In some embodimentsthe gold precursor comprises at least two monodentate ligands comprisingselenium, such as selenium donor ligands. In some embodiments the goldprecursor comprises at least two monodentate ligands comprisingselenium, such as two selenium donor ligands and an alkyl ligand.

In some embodiments the gold precursor may comprise one or moreadditional neutral adducts. Adduct forming ligands may be ethers,polyethers, thioethers, polythioethers, amines or polyamines orderivatives thereof, such THF (tetrahydrofuran), DME (dimethylether),diglyme, dimethylsulfide, 1,2-bis(methylthio)ethane,tetrahydrothiophene, TMEDA (tetramethylethylenediamine), diene, Et₃N,pyridine, quinuclidine or 1-methylpyrrolidine or derivatives thereof.

In some embodiments the gold precursor may comprise two independentlyselected alkyl ligands and a ligand comprising sulfur, such as a sulfurdonor ligand. In some embodiments the ligand comprising sulfur maycomprise a dithiocarbamato ligand. In some embodiments the ligandcomprising sulfur may comprise a thiocarbamato ligand. In someembodiments the ligand comprising sulfur may comprise analkylthiocarbamato ligand, for example a dialkylthiocarbamato ligand. Insome embodiments the ligand comprising sulfur may comprise adialkylthiocarbamato ligand, such as diethylthiocarbamato ligand. Insome embodiments the ligand comprising sulfur may comprise adialkyldithiocarbamato ligand, such as diethyldithiocarbamato ligand. Insome embodiments the gold precursor may comprise diethyldithiocarbamateof dimethylgold(III) (Me₂Au(S₂CNEt₂)). In some embodiments the goldprecursor may comprise thioamidato, beta-thiodiketonato,beta-dithiodiketonato, beta-thioketoiminato, thiocarboksylato, and/ordithiocarboxylato ligands.

In some embodiments the gold precursor may comprise a ligand comprisingsulfur, such as a sulfur donor ligand, and a bidentate ligand, forexample a ligand selected from one of2,2,6,6-tetramethyl-3,5-heptanedionato (thd), hexafluoroacetylacetonato(hfac), and 2,2-dimethyl-6,6,7,7,8,8,8-heptafluorooctane-3,5-dionato(fod). In some embodiments the gold precursor may comprise twoindependently selected alkyl ligands and a carboxylato ligand,thiocarboxylato ligand, or dithiocarboxylato ligand. In some embodimentsthe gold precursor may comprise an alkyl ligand, such as twoindependently selected alkyl ligands and a ligand having the formula SR,wherein R is an independently selected alkyl groups. In some embodimentsthe gold precursor may also comprise a ligand having the formula OR,wherein R is an independently selected alkyl group.

In some embodiments the alkyl ligand of the gold precursor may compriseless than 5, less than 4, less than 3 or less than two carbon atoms. Insome embodiments the alkyl ligand may comprise one carbon atom, such asin Me. In some embodiments the alkyl ligand may comprise two carbonatoms, such as in Et. In some embodiments the alkyl ligand is not asubstituted alkyl ligand.

Second Reactants

In some embodiments the second reactant may comprise oxygen. In someembodiments the second reactant may comprise a reactive species ofoxygen, for example oxygen atoms, oxygen radicals, oxygen ions, and/oroxygen plasma. In some embodiments the second reactant may compriseozone (O₃). In some embodiments the second reactant may comprisemolecular oxygen (O₂) and ozone. In some embodiments the second reactantmay not comprise a compound comprising oxygen other than ozone. In someembodiments the second reactant may comprise nitrogen, for example N₂O.In some embodiments, the second reactant may comprise a peroxide, forexample H₂O₂.

In some embodiments the second reactant may not comprise H₂O. In someembodiments, the second reactant does not comprise a plasma, for examplean oxygen plasma. However, in some other embodiments the second reactantmay comprise reactive species generated by a plasma from a gascomprising oxygen.

In some embodiments the second precursor comprises ozone and less thanabout 50%, 25%, 15%, 10%, 5%, 1%, or 0.1% of impurities other than inertgases.

Thin Film Characteristics

Thin films comprising gold deposited according to some of theembodiments described herein may be continuous thin films comprisinggold. In some embodiments the thin films comprising gold depositedaccording to some of the embodiments described herein may be continuousat a thickness below about 100 nm, below about 60 nm, below about 50 nm,below about 40 nm, below about 30 nm, below about 25 nm, or below about20 nm or below about 15 nm or below about 10 nm or below about 5 nm orlower. The continuity referred can be physically continuity orelectrical continuity. In some embodiments, the thickness at which afilm may be physically continuous may not be the same as the thicknessat which a film is electrically continuous, and the thickness at which afilm may be electrically continuous may not be the same as the thicknessat which a film is physically continuous.

While in some embodiments a thin film comprising gold depositedaccording to some of the embodiments described herein may be continuous,in some embodiments it may be desirable to form a non-continuous thinfilm comprising gold, or a thin film comprising separate islands ornanoparticles comprising gold. In some embodiments the deposited thinfilm comprising gold may comprise nanoparticles comprising gold that arenot substantially physically or electrically continuous with oneanother. In some embodiments the deposited thin film comprising gold maycomprise separate nanoparticles, or separate islands, comprising gold.

In some embodiments a thin film comprising gold deposited according tosome of the embodiments described herein may have a resistivity of lessthan about 20 μΩcm at a thickness of less than about 100 nm. In someembodiments a thin film comprising gold deposited according to some ofthe embodiments described herein may have a resistivity of less thanabout 20 μΩcm at a thickness of below about 60 nm, below about 50 nm,below about 40 nm, below about 30 nm, below about 25 nm, or below about20 nm or lower. In some embodiments a thin film comprising golddeposited according to some of the embodiments described herein may havea resistivity of less than about 15 μΩcm at a thickness of below about60 nm, below about 50 nm, below about 40 nm, below about 30 nm, belowabout 25 nm, or below about 20 nm or lower. In some embodiments a thinfilm comprising gold deposited according to some of the embodimentsdescribed herein may have a resistivity of less than about 10 μΩcm at athickness of below about 60 nm, below about 50 nm, below about 40 nm,below about 30 nm, below about 25 nm, or below about 20 nm or lower. Insome embodiments a thin film comprising gold deposited according to someof the embodiments described herein may have a resistivity of less thanabout 200 μΩcm at a thickness of below about 30 nm, below about 20 nm,below about 15 nm, below about 10 nm, below about 8 nm, or below about 5nm or lower.

In some embodiments a thin film comprising gold deposited according tosome of the embodiments described herein may have a resistivity of lessthan about 200 μΩcm, less than about 100 μΩcm, less than about 50 μΩcm,less than about 30 μΩcm, less than about 20 μΩcm, less than about 18μΩcm, less than about 15 μΩcm, less than about 12 μΩcm, less than about10 μΩcm, less than about 8 μΩcm, or less than about 5 μΩcm or lower at athickness of less than about 100 nm. In some embodiments a thin filmcomprising gold deposited according to some of the embodiments describedherein may have a resistivity of less than about 20 μΩcm, less thanabout 18 μΩcm, less than about 15 μΩcm, less than about 12 μΩcm, lessthan about 10 μΩcm, less than about 8 μΩcm, or less than about 5 μΩcm orlower at a thickness of less than about 50 nm.

In some embodiments a thin film comprising gold deposited according tosome of the embodiments described herein may be crystalline orpolycrystalline. In some embodiments a thin film comprising golddeposited according to some of the embodiments described herein may havea cubic crystal structure.[0088] [0083]In some embodiments a thin filmcomprising gold deposited according to some of the embodiments describedherein may have a thickness from about 20 nm to about 100 nm. In someembodiments a thin film comprising gold deposited according to some ofthe embodiments described herein may have a thickness from about 20 nmto about 60 nm. In some embodiments a thin film comprising golddeposited according to some of the embodiments described herein may havea thickness greater than about 20, greater than about 30 nm, greaterthan about 40 nm, greater than about 50 nm, greater than about 60 nm,greater than about 100 nm, greater than about 250 nm, greater than about500 nm, or greater. In some embodiments a thin film comprising golddeposited according to some of the embodiments described herein may havea thickness of less than about 50 nm, less than about 30 nm, less thanabout 20 nm, less than about 15 nm, less than about 10 nm, less thanabout 5 nm or in some instances the amount of gold corresponds tothickness of less than about 5 nm, less than about 3 nm, less than about2 nm or less than about 1 nm, for example, if a non-continuous film orseparate particles or islands comprising gold are desired.

In some embodiments the growth rate of the film is from about 0.01∈/cycle to about 5 ∈/cycle, from about 0.05 ∈/cycle to about 2 ∈/cycle.In some embodiments the growth rate of the film is more than about 0.1∈/cycle, more than about 0.3 ∈/cycle, more than about 0.5 ∈/cycle, morethan about 0.7 ∈/cycle, more than about 0.8 ∈/cycle, more than about 0.9∈/cycle, more than about 1 ∈/cycle, more than about 1.1 ∈/cycle, or morethan about 1.2 ∈/cycle or more.

In some embodiments a thin film comprising gold may comprise less thanabout 20 at-%, less than about 10 at-%, less than about 7 at-%, lessthan about 5 at-%, less than about 3 at-%, less than about 2 at-%, orless than about 1 at-% of impurities, that is, elements other than Au.In some embodiments the thin film comprising gold comprise less thanabout 20 at-%, less than about 10 at-%, less than about 5 at-%, lessthan about 2 at-%, or less than about 1 at-% of hydrogen. In someembodiments the thin film comprising gold may comprise less than about10 at-%, less than about 5 at-%, less than about 2 at-%, less than about1 at-% or less than about 0.5 at-% of carbon. In some embodiments thethin film comprising gold may comprise less than about 5 at-%, less thanabout 2 at-%, less than about 1 at-%, less than about 0.5 at-%, or lessthan about 0.2 at-% of nitrogen. In some embodiments the thin filmcomprising gold may comprise less than about 15 at-%, less than about 10at-%, less than about 5 at-%, less than about 3 at-%, less than about 2at-%, or less than about 1 at-% of oxygen. In some embodiments the thinfilm comprising gold may comprise less than about 5 at-%, less thanabout 1 at-%, less than about 0.5 at-%, less than about 0.2 at-%, orless than about 0.1 at-% of sulfur. In some embodiments the thin filmcomprising gold may comprise more than about 80 at-%, more than about 90at-%, more than about 93 at-%, more than about 95 at-%, more than about97 at-%, or more than about 99 at-% gold.

In some embodiments the thin films comprising gold may be deposited on athree-dimensional structure. In some embodiments the step coverage ofthe thin film comprising gold may be equal to or greater than about 50%,greater than about 80%, greater than about 90%, about 95%, about 98% orabout 99% or greater in structures having aspect ratios (height/width)of more than about 2, more than about 5, more than about 10, more thanabout 25 or more than about 50.

EXAMPLES Example 1

The thermal properties of diethyldithiocarbamate of dimethylgold(III)(Me₂Au(S₂CNEt₂)) were investigated. Me₂Au(S₂CNEt₂) was found to be asolid at room temperature. When heated, Me₂Au(S₂CNEt₂) was found to meltbetween about 40° C. and about 44° C. As shown in FIG. 3 , thethermogravimetric analysis (TGA) curve for Me₂Au(S₂CNEt₂) (10° C./minheating rate, 10 mg sample size, N₂ flow at 1 atm) shows almost completeevaporation below about 220° C.

Example 2

Thin films comprising gold were deposited by ALD type processesaccording to some embodiments and described herein. Me₂Au(S₂CNEt₂) wasused as the gold precursor and ozone (O₃) was used as the secondreactant. Sample thin films comprising gold were deposited attemperatures of 120° C., 150° C., 180° C., and 200° C. Each thin filmsample was deposited by a deposition process according to someembodiments and as described herein including 500 deposition cycles,each cycle having a gold precursor pulse time of 1 second, a goldprecursor purge time of 1 second, an ozone pulse time of 1 second and anozone purge time of 1 second.

As shown in FIG. 4A, the growth rate, measured in ∈/cycle, increasedwith increasing thin film deposition temperature, from about 0.4 ∈/cycleat 120° C. to about 1.1 ∈/cycle at 200° C.

The sample thin films were found to be uniform, as shown in FIG. 4B. Thethicknesses of each sample thin film comprising gold remainedapproximately uniform over the entirety of the substrate, from adjacentto the precursor inlet of the reaction space to 4.0 cm away from theprecursor inlet. Unlike previous vapor deposition processes based onchemical reactions, such as ALD or CVD, for thin films comprising gold,this uniformity was achieved at very low film thicknesses, from about 20nm to about 60 nm.

The resistivity of the sample thin films was measured, and it was foundthat all of the deposited sample thin films were conductive, as shown inFIG. 4C. The resistivity decreased from about 50 μΩcm at a depositiontemperature of 120° C. to about 5 μΩcm at a deposition temperature of150° C., and remained below about 10 μΩcm for the films deposited at180° C. and 200° C. These results indicated that, unlike previous vapordeposition processes for gold, the deposited sample films comprisinggold were continuous and conductive.

The crystal structure of the deposited sample films was investigated viaX-ray diffraction. As shown in FIG. 4D, the intensity peaks of the X-raydiffractogram show that the sample films had cubic crystal structures atall deposition temperatures, indicating the deposition of metallic gold.

The sample thin films were also investigated using scanning electronmicroscopy, as shown in FIGS. 5A-D. The SEM images show that, unlikeprevious gold vapor deposition methods, the sample thin films comprisinggold were uniform and continuous for all deposition temperatures between120° C. and 200° C. at low thicknesses, from about 20 nm to about 60 nm.The deposited sample thin films comprising gold completely covered thesubstrate at all deposition temperatures between 120° C. and 200° C.

Example 3

Thin films comprising gold were deposited according to ALD typeprocesses according to some embodiments and described herein.Me₂Au(S₂CNEt₂) was used as the gold precursor and ozone (O₃) was used asthe second reactant. The deposition temperature for all sample thinfilms was 180° C. Each thin film sample was deposited by a depositionprocess according to some embodiments and as described herein including500 deposition cycles. The gold precursor and second reactant pulsetimes were varied from 0.5 seconds to 2 seconds, while the purge timeswere held constant at 1 second.

As shown in FIG. 6A, the growth rate, measured in ∈/cycle, saturated ata precursor pulse length of 1 second. This growth rate was found to beabout 0.9 ∈/cycle. The growth rate varied from about 0.8 ∈/cycle toabout 0.9 ∈/cycle for the range of precursor pulse lengths investigated.

As shown in FIG. 6B, the sample thin film comprising gold deposited witha precursor pulse time of 1 second was found to be more uniform than thesample film deposited with a precursor pulse time of 2 seconds. In bothcases, the sample thin films were found to be uniform and continuous atvery low thicknesses, from about 43 nm to about 45 nm.

The resistivity of the sample thin films was measured, and it was foundthat all of the deposited sample thin films were conductive, as shown inFIG. 6C. The resistivity decreased from about 17 μΩcm for a depositionprocess having a precursor pulse time of 0.5 seconds to about 5 μΩcmdeposition process having a precursor pulse time of 2 seconds. It wasfound that the resistivity increased slightly from about 10 μΩcm toabout 12 μΩcm as the precursor pules time increased from 1 second to 1.5seconds. These results indicated that, the deposited sample filmscomprising gold were continuous and conductive.

Example 4

Thin films comprising gold were deposited according to ALD typeprocesses according to some embodiments and described herein.Me₂Au(S₂CNEt₂) was used as the gold precursor and ozone (O₃) was used asthe second reactant. Sample thin films were deposited at a temperatureof 180° C. The number of deposition cycles was varied for each samplefilm, from 50 to 500 cycles. Each deposition cycle had a gold precursorpulse time of 1 second, a gold precursor purge time of 1 second, anozone pulse time of 1 second and an ozone purge time of 1 second.

As shown in FIG. 7A, the sample thin film thicknesses increasedapproximately linearly from less than about 5 nm for a depositionprocess including 50 deposition cycles to about 45 nm for a depositionprocess including 500 deposition cycles.

The sample thin films were also investigated using scanning electronmicroscopy, as shown in FIGS. 7B-D. The SEM images show that, the samplethin film deposited by 500 cycles was uniform and continuous.

Example 5

Sample thin films comprising gold were deposited according to ALD typeprocesses according to some embodiments and described herein.Me₂Au(S₂CNEt₂) was used as the gold precursor and ozone (O₃) was used asthe second reactant. A first sample was prepared with a depositiontemperature 120° C., while a second sample was prepared with adeposition temperature 180° C. Both thin film samples were deposited bya deposition process according to some embodiments and as describedherein including 500 deposition cycles, each cycle having a goldprecursor pulse time of 10 second, a gold precursor purge time of 10second, an ozone pulse time of 10 second and an ozone purge time of 10second.

The first sample thin film comprising gold deposited at 120° C. wasfound to be about 21 nm thick. The second sample thin film comprisinggold deposited at 180° C. was found to be about 47 nm thick. Thecomposition of the thin films was analysed and is shown below inTable 1. No sulfur was detected in either sample film.

TABLE 1 Film composition for two sample thin films comprising golddeposited at 120° C. and 180° C. Composition of film Composition of filmdeposited at 120° C. (at-%) deposited at 180° C. (at-%) Au 91.23 ± 0.99 95.88 ± 0.78  H 2.16 ± 0.57 0.85 ± 0.30 C 0.85 ± 0.19 0.20 ± 0.06 N 0.51± 0.16 0.19 ± 0.08 O 5.25 ± 0.51 2.89 ± 0.29

Language of degree used herein, such as the terms “approximately,”“about,” “generally,” and “substantially” as used herein represent avalue, amount, or characteristic close to the stated value, amount, orcharacteristic that still performs a desired function or achieves adesired result. For example, the terms “approximately”, “about”,“generally,” and “substantially” may refer to an amount that is withinless than or equal to 10% of, within less than or equal to 5% of, withinless than or equal to 1% of, within less than or equal to 0.1% of, andwithin less than or equal to 0.01% of the stated amount. If the statedamount is 0 (e.g., none, having no), the above recited ranges can bespecific ranges, and not within a particular % of the value. Forexample, within less than or equal to 10 wt./vol. % of, within less thanor equal to 5 wt./vol. % of, within less than or equal to 1 wt./vol. %of, within less than or equal to 0.1 wt./vol. % of, and within less thanor equal to 0.01 wt./vol. % of the stated amount.

The terms “film” and “thin film” are used herein for simplicity. “Film”and “thin film” are meant to mean any continuous or non-continuousstructures and material deposited by the methods disclosed herein. Forexample, “film” and “thin film” could include 2D materials, nanorods,nanotubes or nanoparticles or even single partial or full molecularlayers or partial or full atomic layers or clusters of atoms and/ormolecules. “Film” and “thin film” may comprise material or layer withpinholes, but still be at least partially continuous.

It will be understood by those of skill in the art that numerous andvarious modifications can be made without departing from the spirit ofthe present invention. The described features, structures,characteristics and precursors can be combined in any suitable manner.Therefore, it should be clearly understood that the forms of the presentinvention are illustrative only and are not intended to limit the scopeof the present invention. All modifications and changes are intended tofall within the scope of the invention, as defined by the appendedclaims.

What is claimed is:
 1. A process for forming a thin film comprising goldon a substrate in a reaction space, the process comprising: sequentiallycontacting the substrate with a vapor phase organometallic goldprecursor and a vapor phase second reactant, wherein the gold precursorand the second reactant react to form the thin film comprising gold, andwherein the thin film comprising gold has a step coverage of greaterthan 50%.
 2. The process of claim 1, wherein sequentially contacting thesubstrate with a vapor phase organometallic gold precursor and a vaporphase second reactant comprises a deposition cycle that is repeated twoor more times.
 3. The process of claim 2, wherein the deposition cyclefurther comprises removing excess vapor phase organometallic goldprecursor from the reaction space after contacting the substrate withthe vapor phase gold precursor and prior to contacting the substratewith the vapor phase second reactant.
 4. The process of claim 2, whereinthe deposition cycle further comprises removing excess vapor phasesecond reactant and reaction byproducts, if any, from the reaction spaceafter contacting the substrate with the vapor phase second reactant. 5.The process of claim 2, wherein the thin film comprising gold isdeposited at a growth rate of more than about 0.8 Å per depositioncycle.
 6. The process of claim 2, wherein the deposition cycle isrepeated until the thin film comprising gold has a thickness of fromabout 20 nm to about 50 nm.
 7. The process of claim 2, wherein theprocess is an atomic layer deposition (ALD) process.
 8. The process ofclaim 2, wherein the thin film comprising gold is continuous after 100deposition cycles.
 9. The process of claim 1, wherein the gold of theorganometallic gold precursor has an oxidation state of +III.
 10. Theprocess of claim 1, wherein the organometallic gold precursor comprisesat least one alkyl ligand.
 11. The process of claim 1, wherein theorganometallic gold precursor comprises one or more neutral adducts. 12.The process of claim 1, wherein the organometallic gold precursorcomprises a ligand comprising sulfur or selenium.
 13. The process ofclaim 1, wherein the organometallic gold precursor comprises adiethyldithiocarbamato ligand.
 14. The process of claim 13, wherein theorganometallic gold precursor comprises Me₂Au(S₂CNEt₂).
 15. The processof claim 1, wherein the vapor phase second reactant comprises oxygen.16. The process of claim 15, wherein the vapor phase second reactantcomprises a reactive species of oxygen.
 17. The process of claim 16,wherein the vapor phase second reactant comprises ozone.
 18. The processof claim 1, wherein the process is carried out at a depositiontemperature of from about 120° C. to about 220° C.
 19. The process ofclaim 1, wherein the substrate comprises a three-dimensional structurehaving an aspect ratio of more than
 2. 20. The process of claim 1,wherein the thin film comprising gold has a resistivity of less thanabout 20 μΩcm.